ODUk protection tangent rings are generally adopted for service interaction in order to realize end-to-end service protection across two or more ring networks. At present, commonly used ODUk protection tangent rings are an ODUk shared protection ring (ODUk SPRing) tangent rings, and a networking mode is as follows: tangent rings formed by two ODUk SPRings, or tangent rings formed by an ODUk SPRing and an ODUk subnet connection protection ring (ODUk SNCP). FIG. 1 is a schematic networking diagram of tangent rings of two ODUk SPRings in the prior art. Referring to FIG. 1, a first ODUk SPRing and a second ODUk SPRing constitute tangent rings, where the two ODUk SPRings share a node in common (referred to as “intersection node” for short hereinafter), i.e., node F in FIG. 1. The first ODUk SPRing is composed of nodes such as F, G, H, I, J and K, and the second ODUk SPRing is formed by nodes such as A, B, C, D, E and F. Each node in each ODUk SPRing has two working units (referred to as “sending working unit” for short hereinafter) and two protecting units (referred to as “sending protection unit” for short hereinafter) in a sending direction. The sending working units are channels for sending signals normally, and the sending protection units are channels for sending signals replacing the sending working unit when the sending working units fail. Likewise, each node also has two receiving working units and two receiving protection units for receiving signals in a receiving direction.
When a service 1 from node G through node F to node A and a service 2 from node A through node F to node G exist, the interaction method of the ODUk SPRing tangent rings in the prior art is as shown in FIG. 1. Service 1 is sent from the sending working unit of node G to the receiving working unit of node F, and is then sent from the sending working unit of node F to the receiving working unit of node A. The case is similar for service 2.
In general, if the transmission from the sending working unit of node A in the second ODUk SPRing of the tangent rings to node F fails, the second ODUk SPRing need to switch the service transmission, that is, the service on the broken path is switched by node A to a sending protection unit in another sending direction on node A, and is then sent by the sending protection unit to node F, and is then transmitted by the sending working unit of node F to the first ODUk SPRing. At the same time, after switching, service 1 to be sent to the second ODUk SPRing on node F can be sent to node A through node F according to the original path, and may also be sent to node E by the protection unit in another sending direction of node F, and then sent to node A from node E. The state after switching is as shown in FIG. 1(a). Likewise, if the transmission from node G in the first ODUk SPRing to node F fails, the state after switching is as shown in FIG. 1(c). However, if both the transmission from node G in the first ODUk SPRing to node F and the transmission from node A in the second ODUk SPRing to node F fail, the state after switching is as shown in FIG. 1(b).
It can be seen that, for tangent rings, when path breakage occurs on one ring in the tangent rings, two different switching states described above may exist depending on the state of the other ring. For example, when failure occurs between node A and node F in the second ODUk SPRing, two switching states as shown in FIG. 1(a) and FIG. 1(b) may exist. When failure occurs between node G and node F in the first ODUk SPRing, two switching states as shown in FIG. 1(b) and FIG. 1(c) may exist. In the prior art, when path breakage occurs on one of the tangent rings, the state of the other ring needs to be acquired first through interaction by using the APS protocol, that is, to determine whether the other ring also fails, and then select a corresponding switching method according to the state of the other ring. However, the prior art has the following problems.
When switching the first ODUk SPRing in the tangent rings network, interaction need to be first performed by using the APS protocol, and the switching method can only be determined after the state of the second ODUk SPRing is determined. However, the state of the second ODUk SPRing cannot be obtained in real time through the APS protocol, because the state of the second ODUk SPRing can only be determined after all nodes on the ring are interacted by using the APS protocol. This period of time to interact with all nodes on the ring may be very long, so that the switching time is too long to be acceptable for the first ODUk SPRing. If the switching of the first ODUk SPRing is determined before the state of the second ODUk SPRing after interaction by using the APS protocol is obtained, the switching state of the second ring need to be presumed, and the first ring is switched according to this presumption. However, when the switching state of the second ring is actually determined, it may not be the same as the presumed state. As a result, multiple times of switching may occur, thus resulting in errors during switching, thereby the interaction between the tangency rings cannot be realized normally. The same problem exists in the tangent rings formed by the ODUk SPRing and the ODUk SNCP.